Preheat oven to 375°F (190°C). Butter an 8- or 9-inch springform pan or round cake pan and dust lightly with 1 teaspoon unsweetened cocoa powder, tapping out excess. Place a piece of parchment in the bottom if desired for easy removal.

Melt chocolate and butter

Chop the 8 oz chocolate into small pieces. Combine chopped chocolate and 1 cup butter in a heatproof bowl set over a pan of simmering water (double boiler) or microwave in 20–30 second bursts, stirring between bursts, until just melted and smooth. Remove from heat and let cool 3–5 minutes.

Mix sugar and eggs

In a medium bowl, whisk the 1 cup granulated sugar and 5 large eggs until combined and slightly frothy (you can whisk by hand or use a mixer on low). Stir in 1 teaspoon vanilla extract and 1 teaspoon fine salt.

Combine wet and dry

Gradually whisk the melted chocolate-butter mixture into the egg-sugar mixture until smooth and glossy. Sift in 2 tablespoons cocoa powder and whisk until incorporated and batter is homogeneous.

Bake

Pour batter into the prepared pan and smooth the top. Bake at 375°F (190°C) for 18–22 minutes for an 8-inch pan (a 9-inch may take 16–20 minutes) until the edges are set and the center still looks slightly moist — a toothpick inserted near the center should come out with a few moist crumbs, not wet batter.

Cool and remove

Remove cake from oven and let cool on a wire rack for 10 minutes. Run a thin knife around the edge, then release the springform or invert onto a serving plate if desired. Allow to cool to room temperature (about 1 hour) for best texture. Cake can be chilled for 1–2 hours to firm up before serving.

Finishing / Serving

Make whipped cream

Just before serving, pour 1 cup cold heavy cream into a chilled mixing bowl. Add 2 tablespoons confectioners' sugar and 1 teaspoon vanilla extract. Whip with a whisk or electric mixer on medium-high until soft to medium peaks form, about 2–3 minutes. Do not overbeat.

Plate the cake

If the cake was chilled, bring to near room temperature for 10–15 minutes for best flavor. Slice cake into 8 equal pieces. Place a slice on each plate.

Add ice cream and berries

Spoon or scoop about 2 ounces (approx. 1/4 cup) of vanilla ice cream alongside each slice (adjust per preference). Arrange a generous handful of fresh raspberries (about 1/4 cup) next to the slice and ice cream. If desired, toss a few extra raspberries on top of the cake slice.

Top with whipped cream and dust

Add a dollop (about 1–2 tablespoons) of freshly whipped cream atop each slice or beside the ice cream. Lightly dust the cake and plate with the optional 1 teaspoon cocoa powder for presentation.

Serve

Serve immediately so the ice cream remains frozen and the cake has a contrast of warm/room-temperature chocolate with cold ice cream and fresh raspberries.